TWI807702B - Switching power supply and its control chip and control method - Google Patents

Abstract

The invention provides a switching power supply, a control chip and a control method thereof. A control chip for a switching power supply according to an embodiment of the present invention includes: a peak sampling module configured to generate a peak sampling voltage that varies with the input characteristic voltage based on an input characteristic voltage that characterizes the input voltage of the switching power supply; a follower control module configured to generate a reference voltage that varies with the input characteristic voltage based on the peak sampling voltage and is used to compare with an output feedback voltage that characterizes the output voltage of the switching power supply; The sampling voltage of the current of the transistor generates the gate drive voltage. According to the control chip for the switching power supply of the embodiment of the present invention, the output voltage of the switching power supply can be changed with the change of the input voltage, has higher power conversion efficiency, and can effectively reduce the system cost.

Description

Switching power supply and its control chip and control method

The invention relates to the field of circuits, in particular to a switching power supply, a control chip and a control method thereof.

As people become more and more dependent on electrical devices, the demand for electricity has grown dramatically. To meet the demand for electricity, large electrical generators have been constructed. Generally, power generators are located far away from the customers who need the electricity, thus requiring electricity to be transmitted over long distances. With the invention of the induction motor, alternating current was used to transmit power over long distances. One characteristic of alternating circuit power lines is the power factor. The power factor is the ratio of the power delivered and the power actually consumed. In order to efficiently deliver and utilize electrical power, power factor correction equipment is often required.

Various types of power factor correction equipment have been developed and used in the past. However, in these traditional technologies, when the input voltage of the switching power supply is low, since the output voltage of the switching power supply remains unchanged, it will cause damage to components and increase conversion loss, thereby reducing the power conversion efficiency of the system. At the same time, due to the high temperature of the components, in order to meet the temperature rise requirements of the system, a larger heat sink is required.

In order to solve one or more of the above problems, the present invention provides a switching power supply, a control chip and a control method thereof.

A control chip for a switching power supply according to an embodiment of the present invention includes: a peak sampling module configured to generate a peak sampling voltage that varies with the input characteristic voltage based on an input characteristic voltage that characterizes the input voltage of the switching power supply; a follower control module configured to generate a reference voltage that varies with the input characteristic voltage based on the peak sampling voltage and is used to compare with an output feedback voltage that characterizes the output voltage of the switching power supply; The sampling voltage of the current of the transistor generates the gate drive voltage used to control the turn-on and turn-off of the system power MOS field effect transistor, so that the switch The output voltage of the switching power supply varies with the input voltage of the switching power supply.

A control method for a switching power supply according to an embodiment of the present invention, comprising: based on an input characteristic voltage representing an input voltage of a switching power supply, generating a peak sampling voltage that varies with the input characteristic voltage; based on the peak sampling voltage, generating a reference voltage that varies with the input characteristic voltage and used to compare with an output feedback voltage that characterizes the output voltage of the switching power supply; The gate drive voltage of the switching power supply makes the output voltage of the switching power supply change with the input voltage of the switching power supply.

According to the control chip and control method for the switching power supply of the embodiments of the present invention, the output voltage of the switching power supply can be changed with the change of the input voltage of the switching power supply, and has higher power conversion efficiency, especially when the input voltage of the switching power supply is low, a smaller heat sink of the boost switch and a smaller boost inductor can be used, thereby effectively reducing the system cost.

200: switching power supply

202: control chip

210:Peak sampling module

220: with the control module

230:Gate control module

250: Reference voltage generation module

510: Comparator

520: Low-pass filter circuit

610: operator module

620: High-level quasi-clamp element circuit

630: Low-level quasi-clamp element circuit

700: control method

Gate: Gate drive signal

L1: energy storage inductance

M1: System power MOS field effect transistor

NM1: power MOS field effect transistor

OP5: operational amplifier

QR: quasi-resonant signal

R1, R2, R3, R4: resistors

ramp: ramp signal

S101, S102, S103: process

t0, t1, t2, t3, t5: time

VDD: Voltage

Vin: input voltage

vin_p: peak sampling voltage

Vout: output voltage

vref_EA: reference voltage

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the diagrams required in the embodiments of the present invention will be briefly introduced below. For those of ordinary skill in the art, other diagrams can also be obtained based on these diagrams without creative work.

Fig. 1 shows the schematic diagram of traditional switching power supply and its control chip;

FIG. 2 shows a schematic diagram of a switching power supply and a control chip thereof according to an embodiment of the present invention;

FIG. 3 shows a timing diagram of the input characteristic voltage VI, the peak sampling voltage vin_p, the reference voltage vref_EA, and the output voltage Vout in FIG. 2;

FIG. 4 shows a relationship diagram of the variation of the reference voltage vref_EA and the peak sampling voltage vin_p according to an embodiment of the present invention;

5 shows a schematic diagram of an example circuit implementation of a peak sampling module according to an embodiment of the present invention;

FIG. 6 shows a schematic diagram of an example circuit implementation of a follow control module according to an embodiment of the present invention;

FIG. 7 shows a flowchart of a control method for a switching power supply and its control chip according to an embodiment of the present invention.

The characteristics and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the following in conjunction with the drawings and specific embodiments, The present invention is described in further detail. It should be understood that the specific embodiments described here are only configured to explain the present invention, not to limit the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention.

It should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements but also other elements not expressly listed or which are inherent to such process, method, article or apparatus. Without further limitations, an element defined by the word "comprising..." does not exclude the presence of additional same elements in the process, method, article or device comprising said element.

In order to better understand the present invention, the traditional switching power supply and its control chip are firstly introduced below.

FIG. 1 shows a schematic diagram of a traditional switching power supply and its control chip. As shown in Figure 1, a traditional switching power supply includes rectifier diodes D1-D4, input capacitor C1, energy storage inductor L1, system power MOS field effect transistor (for example, metal oxide semiconductor (Metal Oxide Semiconductor, MOS) tube) M1, freewheeling diode D5, output capacitor C2, voltage dividing resistors R1 and R2, and a control chip 100, wherein: voltage dividing resistors R1 and R2 are used to divide the output voltage Vout of the switching power supply to generate a characteristic output The output feedback voltage FB of the voltage Vout; the control chip 100 generates a gate driving voltage based on the output feedback voltage FB, the current sensing voltage CS representing the current flowing through the system power MOS field effect transistor M1, and the reference voltage vref_EA used to compare with the output feedback voltage FB, so as to drive the system power MOS field effect transistor M1 to turn on and off.

Specifically, as shown in FIG. 1 , the control chip 100 includes a demagnetization detection module 101, a timer 102, a reference voltage generation module 103, an error amplifier 104, and a pulse width modulation comparator 105, etc., wherein: the demagnetization detection module 101 detects the slope of the gate drive signal Gate of the system power MOS field effect transistor M1 and outputs a quasi-resonant signal QR to control the conduction of the system power MOS field effect transistor M1; FB is compared with the reference voltage vref_EA generated by the reference voltage generation module 103 and generates an error amplification signal; the pulse width modulation comparator 105 The ramp signal ramp generated by the timer 102 is compared with the error amplifier signal to generate a comparison signal for controlling the shutdown of the system power MOS field effect transistor M1.

In the switching power supply shown in FIG. 1 , since the reference voltage vref_EA generated by the reference voltage generation module 103 is constant, the output voltage Vout of the switching power supply does not vary with the input voltage Vin of the switching power supply. When the output voltage Vout of the switching power supply decreases, the output feedback voltage FB also decreases. At this time, the voltage of the error amplification signal generated by the error amplifier 104 increases, and the energy stored in the energy storage inductor L1 increases, which increases the output energy transmitted to the switching power supply, so that the output voltage Vout increases, and the output feedback voltage FB also increases. After a period of adjustment, when the error amplifier 104 is in a steady state, the output feedback voltage FB is equal to the reference voltage vref_EA.

When the input voltage Vin of the switching power supply is low, since the output voltage Vout of the switching power supply remains unchanged, the parasitic capacitance of the system power MOS field effect transistor M1 will be damaged, and the conversion loss of the system power MOS field effect transistor M1 will increase, which will reduce the power conversion efficiency of the switching power supply.

In order to solve one or more of the above problems, the present invention provides a switching power supply, a control chip and a control method thereof. The switching power supply and its control chip according to the embodiments of the present invention will be described in detail below in conjunction with the drawings.

FIG. 2 shows a schematic diagram of a switching power supply 200 and its control chip 202 according to an embodiment of the present invention. As shown in FIG. 2 , compared with the switching power supply shown in FIG. 1 , the switching power supply 200 according to the embodiment of the present invention adds a resistor R3 and a resistor R4 . Here, the resistor R3 and the resistor R4 divide the input voltage Vin of the switching power supply 200 to generate the input characteristic voltage VI.

As shown in FIG. 2 , the control chip 202 for the switching power supply 200 includes: a peak sampling module 210 configured to generate a peak sampling voltage vin_p that varies with the input characteristic voltage VI based on the input characteristic voltage VI representing the input voltage Vin of the switching power supply 200; a follower control module 220 configured to generate a reference voltage vref_EA that changes with the input characteristic voltage VI based on the peak sampling voltage vin_p and is used to compare with the output feedback voltage FB representing the output voltage Vout of the switching power supply 200 and a gate control module 230 configured to generate a gate drive voltage for controlling the turn-on and turn-off of the system power MOS field effect transistor M1 based on the reference voltage vref_EA, the output feedback voltage FB, and the current sampling voltage CS representing the system power MOS field effect transistor M1 flowing in the switching power supply 200 voltage, so that the output voltage Vout of the switching power supply 200 varies with the input voltage Vin of the switching power supply 200 .

Compared with the control chip 100 shown in FIG. 1 , the control chip 202 according to the embodiment of the present invention adds a peak sampling module 210 and a following control module 220, which can make the output voltage Vout of the switching power supply 200 change with the input voltage Vin of the switching power supply 200, so that the switching power supply 200 has a higher power conversion efficiency, especially when the input voltage Vin of the switching power supply 200 is low, a smaller boost switch heat sink and a smaller boost inductance can be used, thereby effectively The system cost of the switching power supply 200 is reduced.

FIG. 3 shows a timing diagram of the input characteristic voltage VI, the peak sampling voltage vin_p, the reference voltage vref_EA, and the output voltage Vout in FIG. 2 . As shown in Figure 3, between time t0 and t1, the input representative voltage VI rises in a parabolic curve; at time t1, the input representative voltage VI rises to the second threshold voltage V2p; between time t1 and t2, the input representative voltage VI decreases in a parabolic curve; in the time after time t2, the input representative voltage VI rises and falls in a parabolic manner periodically; at time t5, the input representative voltage VI reaches the first threshold voltage V1p.

As shown in Figure 3, from time t0 to t1, the peak sampling voltage vin_p increases in a parabolic curve; from time t1 to t3, the peak sampling voltage vin_p remains unchanged; in the time after time t3, the peak sampling voltage vin_p increases periodically. Specifically, the peak sampling voltage vin_p starts to increase when the input characteristic voltage VI reaches the highest value of VI in the previous waveform, keeps increasing when the input characteristic voltage VI continues to increase, and remains unchanged when the input characteristic voltage VI decreases and has not yet reached the highest value of VI in the previous waveform. In addition, the reference voltage vref_EA, the output voltage Vout of the switching power supply, and the peak sampling voltage vin_p show the same variation law.

FIG. 4 is a graph showing the variation relationship between the reference voltage vref_EA and the peak sampling voltage vin_p according to an embodiment of the present invention. As shown in FIG. 4, when the peak sampling voltage vin_p is less than the first threshold voltage V1p and greater than the second threshold voltage V2p, the reference voltage vref_EA increases with a predetermined slope; when the peak sampling voltage vin_p is less than or equal to the second threshold voltage V2p, the reference voltage vref_EA is the lower clamp voltage V2; when the peak sampling voltage vin_p is greater than or equal to the first threshold voltage V1p, the reference voltage vref_EA is the upper clamp voltage V1.

It can be seen from FIG. 4 that in some embodiments, the following control module 220 can be configured such that when the peak sampling voltage vin_p is less than the first threshold voltage V1p and greater than the second threshold voltage V2p, Calculate the reference voltage vref_EA based on the peak sampling voltage vin_p and the lower clamp voltage V2; when the peak sampling voltage vin_p is less than or equal to the second threshold voltage V2p, use the lower clamp voltage V2 as the reference voltage vref_EA; when the peak sampling voltage vin_p is greater than or equal to the first threshold voltage V1p, use the upper clamp voltage V1 as the reference voltage vref_EA.

FIG. 5 shows a schematic diagram of an example circuit implementation of the peak sampling module 210 according to an embodiment of the present invention. As shown in FIG. 5 , the peak sampling module 210 includes a comparator 510, a charging resistor R1, a power MOS field effect transistor NM1, a discharging resistor R2, and a capacitor C2, wherein: the comparator 510 compares the input characteristic voltage VI with the voltage on the capacitor C2; when the input characteristic voltage VI is higher than the voltage on the capacitor C2, the power MOS field effect transistor NM1 is in the conduction state, and the voltage VDD charges the capacitor C2 through the charging resistor R1; when the input characteristic voltage VI is lower than the voltage on the capacitor C2 When the voltage is high, the power MOS field effect transistor NM1 is in the off state, and the discharge resistor R2 discharges the capacitor C2; when the input characteristic voltage VI is equal to the voltage on the capacitor C2, the voltage on the capacitor C2 is the peak sampling voltage vin_p.

In some embodiments, the resistance of the discharge resistor R2 may be much greater than the resistance of the charge resistor R1, for example, the resistance of the discharge resistor R2 is 10 times or even 100 times that of the charge resistor R1, so as to facilitate the collection of the peak sampling voltage vin_p.

In some embodiments, the peak sampling module 210 may further include a low-pass filter circuit 520 for low-pass filtering the peak sampling voltage vin_p. For example, the low-pass filter circuit 520 may be an RC circuit composed of a resistor R3 and a capacitor C3.

；高位準箝位元電路620和低位準箝位元電路630對基準電壓vref_EA進行箝位，以將基準電壓vref_EA限制在上箝位元電壓V1和下箝位元電壓V2之間。這裡，需要說明的是，運算放大器OP5既用作運算子模組610中的元件也用低位準箝位元電路630中的元件。 FIG. 6 shows a schematic diagram of an example circuit implementation of the follower control module 220 according to an embodiment of the present invention. As shown in FIG. 6, the following control module 220 includes an operation sub-module 610, a high-level clamping element circuit 620, and a low-level clamping element circuit 630, wherein: the operation sub-module 610 calculates the reference voltage vref_EA based on the peak sampling voltage vin_p, for example, vref_EA=vin_p+ΔV, where

; The high-level clamping element circuit 620 and the low-level clamping element circuit 630 clamp the reference voltage vref_EA to limit the reference voltage vref_EA between the upper clamping element voltage V1 and the lower clamping element voltage V2. Here, it should be noted that the operational amplifier OP5 is used not only as a component in the operation sub-module 610 but also as a component in the low-level clamping element circuit 630 .

In some embodiments, as shown in FIG. 2 , the control chip 202 used for the switching power supply 200 may further include a reference voltage generation module 250 for providing the upper clamp element voltage to the following control module 220. Voltage V1 and lower clamp voltage V2.

FIG. 7 shows a flowchart of a control method 700 for a switching power supply according to an embodiment of the present invention. As shown in FIG. 7, a control method 700 for a switching power supply includes:

S101: Based on the input characteristic voltage representing the input voltage of the switching power supply, generate a peak sampling voltage that varies with the input characteristic voltage;

S102: Based on the peak sampling voltage, generate a reference voltage that varies with the input representative voltage and is used to compare with the output feedback voltage representing the output voltage of the switching power supply; and

S103: Based on the reference voltage, the output feedback voltage, and the sampling voltage representing the current flowing through the system power MOS field effect transistor in the switching power supply, generate a gate driving voltage for controlling the turn-on and turn-off of the system power MOS field effect transistor, so that the output voltage of the switching power supply changes with the change of the input voltage of the switching power supply.

It should be noted that other aspects of the control method for the switching power supply are similar to the corresponding aspects of the control chip for the switching power supply, and thus will not be repeated here.

It is to be understood that the invention is not limited to the specific arrangements and processes described above and shown in the drawings. For conciseness, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the sequence of steps after understanding the spirit of the present invention.

The functional blocks shown in the structural block diagrams above can be implemented as hardware, software, firmware or a combination thereof. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), appropriate firmware, a plug-in program, a function card, and the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. Programs or program code segments may be stored on a machine-readable medium or transmitted over a transmission medium or communication link by a data signal carried in a carrier wave. "Machine-readable medium" may include any medium that can store or transmit information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, Read-Only Memory (ROM), flash memory, Erasable Read Only Memory (EROM), magnetic disks, Compact Disc Read-Only Memory (CD-ROM), optical disks, hard disks, fiber optic media, radio frequency (RF) links, and the like. Code snippets can be accessed via Internet, such as Computer networks such as the Internet, Intranet, etc. are downloaded.

It should also be noted that the exemplary embodiments mentioned in the present invention describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above steps, that is to say, the steps may be performed in the order mentioned in the embodiment, or may be different from the order in the embodiment, or several steps may be performed simultaneously.

The above is only a specific implementation of the present invention, and those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process of the system, module and unit described above can refer to the corresponding process in the foregoing method embodiment, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be covered within the protection scope of the present invention.

200: switching power supply

202: control chip

210:Peak sampling module

220: with the control module

230:Gate control module

240: slope signal

250: Reference voltage generation module

AVDD:

C1: input capacitance

C2: capacitance

CMP: PWM Comparator

COMP: loop compensation

CS: current sense voltage

D1~D4: Rectifier diodes

D5: Freewheeling diode

EA: error amplifier

FB: output feedback voltage

Gate: Gate drive signal

GND: chip reference ground

L1: energy storage inductance

M1: System power MOS field effect transistor

OCP: overcurrent protection

OVP: overvoltage protection

Q: D flip-flop positive output

QR: quasi-resonant signal

R: D flip-flop reset terminal

R1, R2, R3, R4: resistors

ramp: ramp signal

S: D flip-flop set terminal

UVLO: undervoltage protection

V1: upper clamp voltage

V2: Lower clamp voltage

VDD: Voltage

VI: input characteristic voltage

Vin: input voltage

Vout: output voltage

vref_EA: reference voltage

Claims (10)

A control chip for a switching power supply, comprising: The peak sampling module is configured to generate a peak sampling voltage that varies with the input representative voltage based on an input representative voltage representing the input voltage of the switching power supply; A follower control module configured to generate a reference voltage that varies with the input representative voltage and is used for comparison with an output feedback voltage representative of the output voltage of the switching power supply based on the peak sampling voltage; and The gate control module is configured to, based on the reference voltage, the output feedback voltage, and the sampling voltage representing the current flowing through the system power MOS field effect transistor in the switching power supply, generate a gate driving voltage for controlling the turn-on and turn-off of the system power MOS field effect transistor, so that the output voltage of the switching power supply varies with the input voltage of the switching power supply. The control chip according to claim 1, wherein the peak sampling module includes a comparator, a charging resistor, a discharging resistor, and a capacitor, wherein: the comparator compares the input representative voltage to the voltage across the capacitor, When the input characteristic voltage is higher than the voltage on the capacitor, the capacitor is charged through the charging resistor, When the input characteristic voltage is lower than the voltage on the capacitor, the capacitor is discharged through the discharge resistor, When the input characteristic voltage is equal to the voltage on the capacitor, the voltage on the capacitor is the peak sampling voltage. The control chip according to claim 2, wherein the resistance of the discharge resistor is greater than the resistance of the charge resistor. The control chip according to claim 2, wherein the peak sampling module further includes: The low-pass filter circuit is configured to perform low-pass filter on the peak sampling voltage. According to the control chip described in claim 1, wherein the follow-up control module includes: The clamping element circuit is configured to clamp the reference voltage to limit the reference voltage between a lower clamping element voltage and an upper clamping element voltage. The control chip according to claim 5, wherein the following control module is further configured to calculate the reference voltage based on the peak sampling voltage and the lower clamping voltage when the peak sampling voltage is less than a first threshold voltage and greater than a second threshold voltage. The control chip according to claim 6, wherein the following control module is further configured such that when the peak sampling voltage is less than or equal to the second threshold voltage, the reference voltage is the lower clamp voltage. The control chip according to claim 7, wherein the following control module is further configured such that when the peak sampling voltage is greater than or equal to the first threshold voltage, the reference voltage is the upper clamp voltage. A switching power supply, comprising the control chip for switching power supply according to any one of Claims 1 to 8. A control method for a switching power supply, comprising: generating a peak sampling voltage varying with the input characterization voltage based on an input characterization voltage representing the input voltage of the switching power supply; Based on the peak sampled voltage, generating a reference voltage varying with the input representative voltage for comparison with an output feedback voltage representative of the output voltage of the switching power supply; and Based on the reference voltage, the output feedback voltage, and the sampling voltage representing the current flowing through the system power MOS field effect transistor in the switching power supply, a gate drive voltage for controlling the turn-on and turn-off of the system power MOS field effect transistor is generated, so that the output voltage of the switching power supply varies with the input voltage of the switching power supply.